<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html><head><title>Help - Sentinel-1</title>



<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<link rel="stylesheet" href="../style.css"></head><body>
<table class="header">
<tbody>
<tr class="header">
<td class="header">&nbsp; TOPSAR Deburst and
Merge<br>
</td>
<td class="header" align="right"><a href="../general/Overview.html"><img src="../images/snap_header.jpg" border="0"></a></td>
</tr>
</tbody>
</table>
<h3>Sentinel-1 TOPSAR Deburst and Merge</h3>
<p class="MsoNormal"><span style="">For the
TOPSAR IW
and EW SLC products, each product consists of one image per swath per
polarization. IW products have 3 swaths and EW have 5 swaths. Each
sub-swath
image consists of a series of bursts, where each burst was processed as
a
separate SLC image. The individually focused complex burst images are
included,
in azimuth-time order, into a single subswath image, with black-fill
demarcation in between, similar to the ENVISAT ASAR Wide ScanSAR SLC
products.</span></p>
<p class="MsoNormal"><span style="">For IW, a
focused
burst has a duration of 2.75 sec and a burst overlap of ~50-100
samples. For
EW, a focused burst has a duration of 3.19 sec. Overlap increases in
range
within a sub- swath.</span></p>
<p class="MsoNormal"><span style="">Images
for all
bursts in all sub-swaths of an IW SLC product are re-sampled to a
common pixel
spacing grid in range and azimuth.<span style="">&nbsp;
</span>Burst
synchronisation is ensured for both IW and EW products.</span></p>
<p class="MsoNormal"><span style="">Unlike
ASAR WSS
which contains large overlap between beams, for S-1 TOPSAR, the imaged
ground
area of adjacent bursts will only marginally overlap in azimuth just
enough to
provide contiguous coverage of the ground. This is due to the one
natural
azimuth look inherent in the data.</span></p>
<p class="MsoNormal"><span style="">For GRD
products, the bursts are concatenated
and sub-swaths are merged to form one image. Bursts overlap minimally
in
azimuth and sub-swaths overlap minimally in range. Bursts for all beams
have
been resampled to a common grid during azimuth post-processing.</span>&nbsp;</p>
<p class="MsoNormal"><span style="" lang="EN-GB">In the range
direction, for each line in all sub-swaths with the same time tag,
merge
adjacent sub-swaths. For the overlapping region in range, merging is
done midway between subswaths.</span></p>
<p class="MsoNormal"><span lang="EN-GB">In the azimuth
direction, bursts are merged according to their zero Doppler time. Note
that
the black-fill demarcation is not distinctly zero at the end or start
of the
burst. Due to resampling, the data fades into zero and out. The merge
time is
determined by the average of the last line of the first burst and the
first line
of the next burst. For each range cell, the merging time is quantised
to the
nearest output azimuth cell to eliminate any fading to zero data.</span>
</p>
<h4>Input <br>
</h4>



<ul>
<li>The input to the operator is the Sentinel-1 TOPSAR IW or EW SLC product.
The product could be original Sentinel-1 product or processed product.
It could have multi subswaths or just one subswath like in the scae of
split product.<br>
  </li>
</ul>

<h4>Output <br>
</h4>




<ul>
<li>The output of this operator is the deburst product. <br>

  </li>
</ul>


<h4>Parameters Used<br>
</h4>




<ul>
<li>Polarisations: The polarisations for the deburst product. User can select one or more polarisations.<br>

  </li>
</ul>


<p><img style="width: 450px; height: 450px;" alt="" src="images/Deburst.jpg"><br>

</p>

<hr>
</body></html>